[gentoo-user] virtual/shadow

[gentoo-user] virtual/shadow

[Bruce Hill, Jr.]

 These virtual apps are irritating me, and the fanboi answers in #gentoo
are worse.

What is the purpose of virtual/shadow and why would I want it?

Today's update output:

server ~ # emerge -aDjNquv world
[ebuild  N    ] virtual/shadow-0

Would you like to merge these packages? [Yes/No] No

Quitting.

--
Happy Penguin Computers    >`)
126 Fenco Drive            ( \
Tupelo, MS 38801            ^^
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support at happypenguincomputers dot com
http://www.happypenguincomputers.com

Re: [gentoo-user] virtual/shadow

[Paul Hartman]

On Mon, Mar 12, 2012 at 1:05 PM, Bruce Hill, Jr.
<daddy@happypenguincomputers.com> wrote:
>  These virtual apps are irritating me, and the fanboi answers in #gentoo
> are worse.
>
> What is the purpose of virtual/shadow and why would I want it?

Virtual packages are kind of an abstraction layer for compatible
alternative packages. Other packages can depend on the virtual instead
of depending on every combination of possible alternatives, and the
user can install whichever of the alternatives he prefers.

For example, MariaDB is a drop-in replacement for MySQL. From a
dependency standpoint, they are compatible. Instead of any program
depending on MySQL being modified to check for either MySQL or
MariaDB, virtual/mysql was created and it can be satisfied by either
dev-db/mysql or dev-db/mariadb being installed.

In the case of shadow, he new virtual is to allow you to use either
sys-apps/shadow or sys-apps/hardened-shadow. See here:
http://www.gossamer-threads.com/lists/gentoo/dev/249394

If you view the virtual package's ebuild, this line is the key:
RDEPEND="|| ( >=sys-apps/shadow-4.1 sys-apps/hardened-shadow )"


HTH :)

[gentoo-user] Re: virtual/shadow

[Nikos Chantziaras]

On 12/03/12 20:05, Bruce Hill, Jr. wrote:
>   These virtual apps are irritating me, and the fanboi answers in #gentoo
> are worse.
>
> What is the purpose of virtual/shadow and why would I want it?

Paul's answers covers it, but I'll give an explanation that is the 
reverse of a fanboi answer.

The reason we need virtuals is because of a shortcoming in portage: lack 
of "provides" functionality.  RPM packages can tell the package manager 
what they provide.  For example, RPMs for libav and ffmpeg can both use 
"ffmpeg" as their "provides" field.  Portage can't do that, so it needs 
a new "virtual/ffmpeg" package instead.

Re: [gentoo-user] virtual/shadow

[Bruce Hill, Jr.]

On March 12, 2012 at 2:50 PM Paul Hartman <paul.hartman+gentoo@gmail.com>
wrote:

> On Mon, Mar 12, 2012 at 1:05 PM, Bruce Hill, Jr.
> <daddy@happypenguincomputers.com> wrote:
> >  These virtual apps are irritating me, and the fanboi answers in
#gentoo
> > are worse.
> >
> > What is the purpose of virtual/shadow and why would I want it?
>
> Virtual packages are kind of an abstraction layer for compatible
> alternative packages. Other packages can depend on the virtual instead
> of depending on every combination of possible alternatives, and the
> user can install whichever of the alternatives he prefers.
>
> For example, MariaDB is a drop-in replacement for MySQL. From a
> dependency standpoint, they are compatible. Instead of any program
> depending on MySQL being modified to check for either MySQL or
> MariaDB, virtual/mysql was created and it can be satisfied by either
> dev-db/mysql or dev-db/mariadb being installed.
>
> In the case of shadow, he new virtual is to allow you to use either
> sys-apps/shadow or sys-apps/hardened-shadow. See here:
> http://www.gossamer-threads.com/lists/gentoo/dev/249394
>
> If you view the virtual package's ebuild, this line is the key:
> RDEPEND="|| ( >=sys-apps/shadow-4.1 sys-apps/hardened-shadow )"
>
>
> HTH :)
>


Thanks for the kind explanation. I didn't realize hardened was not a
profile (selinux is) and wondered why anything to do with hardened would
even show up on my system(s).
--
Happy Penguin Computers    >`)
126 Fenco Drive            ( \
Tupelo, MS 38801            ^^
662-269-2706; 662-491-8613
support at happypenguincomputers dot com
http://www.happypenguincomputers.com

Re: [gentoo-user] Re: virtual/shadow

[Bruce Hill, Jr.]

On March 12, 2012 at 3:19 PM Nikos Chantziaras <realnc@gmail.com> wrote:

> On 12/03/12 20:05, Bruce Hill, Jr. wrote:
> >   These virtual apps are irritating me, and the fanboi answers in
#gentoo
> > are worse.
> >
> > What is the purpose of virtual/shadow and why would I want it?
>
> Paul's answers covers it, but I'll give an explanation that is the
> reverse of a fanboi answer.
>
> The reason we need virtuals is because of a shortcoming in portage: lack
> of "provides" functionality.  RPM packages can tell the package manager
> what they provide.  For example, RPMs for libav and ffmpeg can both use
> "ffmpeg" as their "provides" field.  Portage can't do that, so it needs
> a new "virtual/ffmpeg" package instead.
>
>


My only experience building software was making scripts to work on my own
computer(s), which didn't require checking deps for everybody and his
brother's possible setups; so frequently portage offends me with it's dep
checking and installing.

Thanks for the patience, guys. My mind has not morphed to The Gentoo Way
(R) yet and frequently bucks up against this type of pkg mgr.
--
Happy Penguin Computers    >`)
126 Fenco Drive            ( \
Tupelo, MS 38801            ^^
662-269-2706; 662-491-8613
support at happypenguincomputers dot com
http://www.happypenguincomputers.com

Re: [gentoo-user] Re: virtual/shadow

[Alan McKinnon]

On Mon, 12 Mar 2012 21:19:12 +0200
Nikos Chantziaras <realnc@gmail.com> wrote:

> On 12/03/12 20:05, Bruce Hill, Jr. wrote:
> >   These virtual apps are irritating me, and the fanboi answers in
> > #gentoo are worse.
> >
> > What is the purpose of virtual/shadow and why would I want it?
> 
> Paul's answers covers it, but I'll give an explanation that is the 
> reverse of a fanboi answer.
> 
> The reason we need virtuals is because of a shortcoming in portage:
> lack of "provides" functionality.  RPM packages can tell the package
> manager what they provide.  For example, RPMs for libav and ffmpeg
> can both use "ffmpeg" as their "provides" field.  Portage can't do
> that, so it needs a new "virtual/ffmpeg" package instead.
> 
> 

Anyone care to offer an opinion on what it will take to get PROVIDES
support in portage?



-- 
Alan McKinnnon
alan.mckinnon@gmail.com

[gentoo-user] Re: virtual/shadow

[»Q«]

On Mon, 12 Mar 2012 22:29:10 +0200
Alan McKinnon <alan.mckinnon@gmail.com> wrote:

> Anyone care to offer an opinion on what it will take to get PROVIDES
> support in portage?

IMO, it would take virtuals causing so many headachy breakages that
some devs started keeping up a steady drumbeat on irc and mailing
lists.  When the number of virtual packages gets close to a thousand,
I'd guess that might happen.  Then there would be years of discussion
and GLEP proposals, and by EAPI 207 it should be done.

;)

[gentoo-user] Re: virtual/shadow

[Nikos Chantziaras]

On 13/03/12 00:34, »Q« wrote:
> On Mon, 12 Mar 2012 22:29:10 +0200
> Alan McKinnon<alan.mckinnon@gmail.com>  wrote:
>
>> Anyone care to offer an opinion on what it will take to get PROVIDES
>> support in portage?
>
> IMO, it would take virtuals causing so many headachy breakages that
> some devs started keeping up a steady drumbeat on irc and mailing
> lists.  When the number of virtual packages gets close to a thousand,
> I'd guess that might happen.  Then there would be years of discussion
> and GLEP proposals, and by EAPI 207 it should be done.

The problem isn't the amount of virtuals.  This doesn't affect the users 
much.  It's the inability for people to offer replacement packages in 
overlays.

Re: [gentoo-user] Re: virtual/shadow

[Neil Bothwick]

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On Tue, 13 Mar 2012 01:54:30 +0200, Nikos Chantziaras wrote:

> >> Anyone care to offer an opinion on what it will take to get PROVIDES
> >> support in portage?  
> >
> > IMO, it would take virtuals causing so many headachy breakages that
> > some devs started keeping up a steady drumbeat on irc and mailing
> > lists.  When the number of virtual packages gets close to a thousand,
> > I'd guess that might happen.  Then there would be years of discussion
> > and GLEP proposals, and by EAPI 207 it should be done.  
> 
> The problem isn't the amount of virtuals.  This doesn't affect the
> users much.  It's the inability for people to offer replacement
> packages in overlays.

They could include a modified virtual in the overlay, but your point is
valid; including the information in the ebuilds is more flexible.


-- 
Neil Bothwick

Light travels faster than sound. This is why some people appear bright
until you hear them speak.

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[gentoo-user] Re: virtual/shadow

[Nikos Chantziaras]

On 13/03/12 02:23, Neil Bothwick wrote:
> On Tue, 13 Mar 2012 01:54:30 +0200, Nikos Chantziaras wrote:
>
>>>> Anyone care to offer an opinion on what it will take to get PROVIDES
>>>> support in portage?
>>>
>>> IMO, it would take virtuals causing so many headachy breakages that
>>> some devs started keeping up a steady drumbeat on irc and mailing
>>> lists.  When the number of virtual packages gets close to a thousand,
>>> I'd guess that might happen.  Then there would be years of discussion
>>> and GLEP proposals, and by EAPI 207 it should be done.
>>
>> The problem isn't the amount of virtuals.  This doesn't affect the
>> users much.  It's the inability for people to offer replacement
>> packages in overlays.
>
> They could include a modified virtual in the overlay, but your point is
> valid; including the information in the ebuilds is more flexible.

This only works if portage has a virtual.  If it doesn't, you're 
screwed.  You need to also provide modified packages of all ebuilds 
depending on the package you're offering a replacement for.  As you can 
guess, it's not practical.

This leaves only one option; have users put the original package in 
package.provided and emerge your replacement as a non-dep (going in 
"world".)

[gentoo-user] Re: virtual/shadow

[»Q«]

On Tue, 13 Mar 2012 01:54:30 +0200
Nikos Chantziaras <realnc@gmail.com> wrote:

> On 13/03/12 00:34, »Q« wrote:
> > On Mon, 12 Mar 2012 22:29:10 +0200
> > Alan McKinnon<alan.mckinnon@gmail.com>  wrote:
> >  
> >> Anyone care to offer an opinion on what it will take to get
> >> PROVIDES support in portage?  
> >
> > IMO, it would take virtuals causing so many headachy breakages that
> > some devs started keeping up a steady drumbeat on irc and mailing
> > lists.  When the number of virtual packages gets close to a
> > thousand, I'd guess that might happen.  Then there would be years
> > of discussion and GLEP proposals, and by EAPI 207 it should be
> > done.  
> 
> The problem isn't the amount of virtuals.  This doesn't affect the
> users much. 

I expect more virtuals will mean more bugs affecting users.  I don't
know how hairy they will be, but here's one ugly example:
<https://bugs.gentoo.org/show_bug.cgi?id=398295>.  It's unresolved, but
less has been added back to @system so stage 3 tarballs aren't broken
for now.  (I guess this could have happened with provides as well.)

> It's the inability for people to offer replacement
> packages in overlays.

Yeah, I see.